The present invention relates generally to hydraulic bottomhole motors for drilling holes in the course of prospecting for or producing oil, gas and other minerals and, more particularly, it relates to turbo-drills.
There is known in the prior art a tubo-drill (cf. U.S. patent application No. 174,861 of Aug. 26, 1971; British patent application No. 41,192 of Sept. 3, 1971) for drilling holes, comprising: a housing having stators secured therein and provided with races and vanes forming guiding channels for passing therethrough a flushing fluid; rotors provided with races and vanes directed oppositely with respect to the stator vanes, whereby the flow of the flushing fluid through the turbo-drill rotates the rotor in relation to the stator; a shaft having a plurality of rotors and disposed in the housing on supports; a supporting unit transmitting force from a string of drill pipes to a drilling bit; bodies of rolling disposed in carriers connected to the shaft, and located between the races of the stators and rotors so as to form together with the carriers, stators and rotors reduction stages forming an axial reduction tubine wherein between the rotors which are an inner driving wheel of the reduction turbine and the stators which are an outer wheel of the tubine, are disposed bodies of rolling which during rotation of the rotors will roll under the action of contact frictional forces and, since the diameter of the race of the inner driving wheel of the reduction turbine is smaller than that of the outer wheel of the turbine, the speed of rotation of the drilling bit is reduced in relation to the speed of rotation of the rotor.
The races of the rotors are disposed in their operative position higher than the respective races of the stators, whereby the bodies of rolling acted upon by a downwardly directed axial force developing on the rotors in the course of translatory motion of the flushing fluid through the reduction stages of the turbine are pressed against the races of the stators and rotors, thereby developing contact frictional forces transmitting the torque to the drilling bit.
During operation of the said turbo-drill which is provided with a turbine having a low pressure differential on the vanes of the rotors and stators, there may occur slippage of the bodies of rolling, which disadvantage reduces reliability of operation of the reduction turbine and efficiency of the turbo-drill.